water to steam

sparc

Hi all,

I am looking to find out how much water expands when it turns to steam at the same pressure. like if you have an open pot with water boiling on the stove. if you took one ounce of that water how much steam does it turn into? I have searched the internet and come up with various answers which are close but not the same. I've found reference to 1647 times, 1689, and over 1700. So which is right or none of them?

Astronuc

At 212°F, 14.7 psia, liquid water has a specific volume of 0.016716 ft³/lbm and steam has a specfic volume of 26.80 ³/lbm, which is a volume ratio of ~1603 : 1 of steam:water.

Ref: http://www.eas.asu.edu/~holbert/eee463/SteamTable.pdf

sparc

Thank you for your assistance, that's what i was looking for, though the ratio is lower than i found elsewhere for 14.7 psia. any idea why there is such a wide range of 'correct' answers to this condition? It seems that it would be straight forward and the answer should be consistent for the same conditions.

Astronuc

I really don't know unless those values do not account for the thermal expansion of the liquid water.

For example, water at 80°F has a specific volume of 0.016073 ft³/lbm so the liquid water at 212°F with a specific volume of .016716 ³/lbm has volume of 1.04 times that of water at 80°F, and the steam at 212°F has then 1667 times the volume of liquid water at 80°F.

The steam to water volume ratio depends on which reference temperature one selects for the water and the ambient pressure.